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Dr Ata Shakeri, Hemmat Nasiri, ,
Volume 7, Issue 1 (8-2021)
Volume 7, Issue 1 (8-2021)
Abstract
Introduction
Pollution sources are basically divided into two groups: geogenic and anthropogenic. Geogenic sources include pollution from geological formations, mineral indices, mineral springs, brackish and saline water sources, and industrial activities, transportation, using agricultural fertilizers, mining activities, and wastes and effluents can be mentioned as anthropogenic pollution sources. Essential nutrients and other metals may enter the food web through the soil. The natural concentration of potentially toxic elements in the soil is usually low, except in the case of soils composed of ore minerals. The amount of trace elements in soils can also increase sharply due to human activities. In recent years, industrial and agricultural development in Iran has grown exponentially and various researches have been focused on assessment of environmental pollution. Therefore, it is necessary to use a set of different quantitative and qualitative methods of soil pollution assessment to gain a better understanding of the extent of pollution. Regarding the pollution of Khiavachay River in Sabalan geothermal region by natural springs and Meshginshahr iron mine, and due to irrigation of arable lands by this river, the aim of this study was to evaluate the pollution of arsenic, cobalt, lead, zinc, copper, iron, manganese and chromium using geochemical indices and statistical methods in the surface soil of Meshginshahr city.
Material and methods
A total of 14 soil samples (0-20 cm) were collected using composite sampling method from agricultural lands irrigated by the water of Khiavachay River. The samples were dried at room temperature, then a part of them passed through a 230 mesh sieve for digestion by four acids and elemental analysis by induction coupled plasma mass spectrometer (ICP-MS) in Zarazma laboratory. In this study, Geo-accumulation index (Igeo), contamination factor (CF) and enrichment factor (EF) were used to determine the severity of soil contamination with heavy metals. Also, in order to investigate how the elements relate to each other and also to determine their origin, the results were analyzed using statistical analysis. Descriptive statistics, correlation coefficient and principal component analysis were performed using SPSS 20 software.
Results and discussion
Comparison of the concentration of elements in the region with their world average in soils and Earth crust shows that the average concentrations of arsenic, zinc and phosphorus in the agricultural soil of Meshginshahr are higher than their values in the world soil and Earth crust. Among the studied elements, As, P and Fe with values of 68.61, 34.27 and 30.76% respectively show the highest coefficients of variation in the region. The high variation coefficient, especially for As, indicates high concentration differences in different parts of the study area and possibly differences in the source of the contaminant. The results show that the amount of arsenic in the soil of station S1 (Moil village, adjacent to the iron mine) is in the range of severe to extremely polluted (Igeo level is 4.62). It is also present in 78% of the collected samples (11 samples) in the range of moderate to severe contamination (Igeo level between 2.37 to 2.95) and in two stations in the range of moderate contamination (Igeo level between 1.79 to 1.87). Zinc is in the moderate contamination range at all sampling points (CF between 1.04 and 2.27). Iron, lead and copper are in both the medium and low pollution ranges, and cobalt, chromium and manganese are only in the low pollution range. Therefore, the region shows significant enrichment to arsenic. These results are in good agreement with the previous study on the Khiavachay River and are reasonable considering the type of formations and irrigation of agricultural lands with arsenic-contaminated water. The results obtained from the pollution indices indicate that the maximum arsenic pollution is present in station number one and close to the iron mine of Moil village. High correlation of arsenic with iron (r = 0.911) and lead (r = 0.637) and its negative correlation with phosphorus (r = -0.65) was observed. The negative correlation of arsenic with phosphorus can be due to the competition of these two elements in the form of anions (arsenate and phosphate) in adsorption by soil colloids. Among the iron ores of the region, the highest concentration of arsenic has been measured in limonite. In the process of limonite formation, insoluble free hydride is formed by the oxidation of divalent iron, and during this reaction, arsenic, which originates from hot springs and hydrothermal waters of the region, is co-precipitated with iron. Therefore, As in the Moil iron mine has secondarily deposited in limonite under the influence of geothermal resources and hot springs. The results of correlation coefficient have been confirmed by principal component analysis.
Conclusion
Existence of hydrothermal springs with high concentration of arsenic, which are considered as causes of water pollution in Khiavachay River, and irrigation of agricultural lands with river water are important factors of arsenic enrichment in the soil of the region. Considering the amount of geo-accumulation index, the soil of the study area has moderate to severe As contamination. The results of the enrichment factor indicate significant enrichment for As and moderate enrichment for P, which is influenced by geological formations and natural factors for arsenic and anthropogenic factors for phosphorus. The results of statistical analyzes showed the important role of Moil iron mine and hydrothermal springs in the region in increasing the concentration of As, iron and lead in the soil of the region. Considering the negative effects of soil pollutants on the environment and due to the high concentration of arsenic in the study area, it seems necessary to study the concentration of this element in crops in the region and assess the health risk. For this purpose, evaluation of mobility and bioavailability of elements by sequential extraction methods, study of the role of soil physicochemical parameters in elemental mobility and investigation of the role of plant species in the uptake of pollutants from soil can be of great help in better analysis of the results.
Mahsa Saadat Gohari, Dr Afshin Qishlaqi,
Volume 8, Issue 1 (9-2022)
Volume 8, Issue 1 (9-2022)
Abstract
The aim of this study is to determine the ambient concentration, content of heavy metals and morphology and mineralogy of PM2.5 samples collected from air pollution monitoring station in Haft-Tir square (central Tehran). For this purpose, PM2.5 samples were collected by means of low-volume sampling device during five months (April-August 2019). Based on the obtained results, there is more loading of PM2.5 on June higher that 10 μgm−3 and showed high to very high pollution level. Variations in metal concentration in the sampling months were relatively similar, showing order of Zn>Ni>Pb>Cr>Cu>Cd. Comparing the mean concentration of metals with international permissible limits the concentration of Pb and Cr in PM2.5 samples was lower than that of recommended by the WHO while the average concentration of Cd and Ni was higher than those of USEPA recommended limit. Calculations of enrichment factor and results of principal component analysis revealed that Cr is of geogenic origin, Cd and Zn are derived from anthropic sources and Pb, Cu and Ni are probably of mixed sources. Based on scanning electron microscopy images, PM2.5 are observed as a shapeless or irregular, rod-shaped, irregular spherical, completely spherical, sheeted, as well as long chain aggregates or single crystals. According to the results of X-ray diffraction analysis, clay minerals, quartz and calcite were found as major minerals, gypsum and dolomite minerals were identified as minor minerals and wüstite and halite minerals were identified as rare mineral phases.
Dr. Tahereh Azari, Mrs Marzieh Touri Kadar-Ghale, Dr. Fatemeh Kardel,
Volume 9, Issue 1 (9-2023)
Volume 9, Issue 1 (9-2023)
Abstract
The infiltration of leachate resulting from waste disposal into the ground and reaching the groundwater aquifers leads to the pollution of groundwater resources. Considering the importance of water resources in the critical situation of Iran, it is necessary to carry out serious research to protect the existing resources. This research is a case study to simulate the process of leakage and transfer of leachate from landfill to groundwater and the spread and migration of four heavy metals (lead, iron, zinc and cadmium) in the unconfined alluvial aquifer of Babolsar city. The 5 ha landfill investigated in this study receives 150 tons of solid waste per day from Babolsar city. Infiltration and transfer of leachate to this aquifer is simulated using finite difference technique and MODFLOW, MT3DMS codes in GMS software. After the implementation and calibration of the quantitative model, the qualitative model was implemented for four heavy metals (lead, iron, zinc and cadmium). By applying the processes of convection, hydrodynamic dispersion and absorption, the natural cleaning potential of each element was investigated and the qualitative model of pollutant transport was calibrated and the amount and rate of absorption in the studied range were determined for each element. Based on the simulation results, the structure and geological material have had the greatest impact on the transfer of leachate from municipal solid waste in the traditional landfill in Babolsar. Due to their low permeability and high capacity to absorb contaminants, clay and organic matter in the soil of the studied area have prevented the transmission and spread of pollution plume in the alluvial aquifer of Babolsar. In order to predict the potential of natural cleaning of the aquifer in the coming years and determine the fate of these elements, the graph of changes in the concentration of these elements until they reach the standard allowed concentration was drawn with respect to time and the equation for each element was determined. The cleaning equations obtained from the qualitative model are a suitable tool for predicting the development of the pollution plume in the aquifer and determining the natural changes in the concentration of these elements with time for the optimal management of the aquifer in the hands of experts.
Ms Zahra Yaftian, Dr Ata Shakeri, Dr Mehrdad Hadipourdeshal, Dr Meisam Rastegari Mehr,
Volume 9, Issue 2 (12-2023)
Volume 9, Issue 2 (12-2023)
Abstract
Mining is a necessary activity for the development of countries, but it imposes direct and indirect negative impacts on the exploited areas and their surroundings. Sangan iron mine is one of the largest iron ore deposits in the Middle East, where the ore is extracted by open pit mining. The present study aims to investigate the soil’s concentration of heavy metals and to assess the level of soil’s contamination in the Sangan mining area. For these purposes, 44 samples of the soils (including both topsoils and subsoils) of the Sangan mining area were collected, and were analyzed by an ICP-MS device. The obtained data were analyzed by calculating the geochemical indices and statistical methods. On the basis of descriptive statistics of the analytical data, Pb with an average content of 138.39 mg/kg and Cd with an average concentration of 0.19 mg/kg had the highest and lowest concentrations in top soils, respectively. Moreover, Cr with an average value of 102.19 mg/kg, showed the highest, and Cd with an average of 0.2 mg/kg showed the lowest concentrations in subsoils. The average concentrations of As, Cr and Fe in the study area were higher than their respective values in the World-Soil Average composition. Among the elements, Pb had very high and severe enrichment in two stations with enrichment factor values of 149 and 23.85. The results indicated no severe soil pollution and ecological risk in the study area, except in some sampling sites. The most polluted soils were collected near the placer extraction units and tailing ponds of Ehya-Sepahan Company, as well as the waste rock pile of Sanabad Comprehensive Development Industrial and Mining Company.
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